//
// Mono.Security.Cryptography.CryptoTools
//	Shared class for common cryptographic functionalities
//
// Authors:
//	Sebastien Pouliot <sebastien@ximian.com>
//
// (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
// Copyright (C) 2004, 2006 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.Security.Cryptography;

namespace Mono.Security.Cryptography
{

	public sealed class KeyBuilder
	{
		static private RandomNumberGenerator rng;

		private KeyBuilder()
		{
		}

		static public byte[] Key(int size)
		{
			if (rng == null)
				rng = RandomNumberGenerator.Create();

			byte[] key = new byte[size];
			rng.GetBytes(key);
			return key;
		}

		static public byte[] IV(int size)
		{
			if (rng == null)
				rng = RandomNumberGenerator.Create();

			byte[] iv = new byte[size];
			rng.GetBytes(iv);
			return iv;
		}
	}

	// Process an array as a sequence of blocks
	public class BlockProcessor
	{
		private ICryptoTransform transform;
		private byte[] block;
		private int blockSize;	// in bytes (not in bits)
		private int blockCount;

		public BlockProcessor(ICryptoTransform transform)
			: this(transform, transform.InputBlockSize) { }

		// some Transforms (like HashAlgorithm descendant) return 1 for
		// block size (which isn't their real internal block size)
		public BlockProcessor(ICryptoTransform transform, int blockSize)
		{
			this.transform = transform;
			this.blockSize = blockSize;
			block = new byte[blockSize];
		}

		~BlockProcessor()
		{
			// zeroize our block (so we don't retain any information)
			Array.Clear(block, 0, blockSize);
		}

		public void Initialize()
		{
			Array.Clear(block, 0, blockSize);
			blockCount = 0;
		}

		public void Core(byte[] rgb)
		{
			Core(rgb, 0, rgb.Length);
		}

		public void Core(byte[] rgb, int ib, int cb)
		{
			// 1. fill the rest of the "block"
			int n = System.Math.Min(blockSize - blockCount, cb);
			Buffer.BlockCopy(rgb, ib, block, blockCount, n);
			blockCount += n;

			// 2. if block is full then transform it
			if (blockCount == blockSize)
			{
				transform.TransformBlock(block, 0, blockSize, block, 0);

				// 3. transform any other full block in specified buffer
				int b = (int)((cb - n) / blockSize);
				for (int i = 0; i < b; i++)
				{
					transform.TransformBlock(rgb, n + ib, blockSize, block, 0);
					n += blockSize;
				}

				// 4. if data is still present fill the "block" with the remainder
				blockCount = cb - n;
				if (blockCount > 0)
					Buffer.BlockCopy(rgb, n, block, 0, blockCount);
			}
		}

		public byte[] Final()
		{
			return transform.TransformFinalBlock(block, 0, blockCount);
		}
	}
}
